This invention relates to a shift control device for vehicular transmissions and more particularly to an improved and simplified interlock system between the shifting mechanisms of primary and auxiliary transmissions.
There have been proposed a variety of off the road vehicles having three or four wheels and large, low pressure balloon tires. A large number of these vehicles are designed to accommodate only a single rider and employ as their power unit an engine, transmission assembly of the type commonly associated with motorcycles. Such engine, transmission assemblies include a crankcase which not only contains the crankshaft of the engine but also a primary change speed transmission. Such motorcycle transmissions, however, do not have the wide variety of speed ratios that are desirable for off the road use nor do they accommodate a reverse gear. Therefore, it has been the practice to employ auxiliary transmissions having their input shafts driven by the primary transmission output shaft and which include either plural speed ratios and/or a reversing gear. In this way, it is possible to obtain a very compact power unit consisting of the engine and transmission while providing a great number of speed ratios and also reverse gear.
Where two such transmissions are employed, it is desirable to incorporate an interlock mechanism so that the auxiliary transmission cannot be shifted into reverse when the primary transmission is in a high speed ratio or vice versa. This is advantageous so as to insure that the vehicle will not be operated at too great a speed in reverse.
Like the transmission itself, it is desirable that the interlock by very simple and compact in configuration bearing in mind the overall compact nature of the vehicles with which this type of transmission are employed. However, even though the device must be compact, it should be foolproof in operation and should insure that the device cannot malfunction. The device also should be constructed in such a way that the interlock itself does not interfere with the normal desired shifting pattern of either or both of the primary and auxiliary transmission units. Devices of the type previously proposed have not achieved these results completely.
It is, therefore, a principal object of this invention to provide an improved and simplified interlock relationship between primary and auxiliary transmissions of a vehicle.
It is a further object of this invention to provide a simple, compact and foolproof interlock device for a vehicle transmission.
It is yet a further object of this invention to provide an interlock mechanism for preventing inadvertent shifting of one transmission when the other transmission is in predetermined speed ratios.